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OREKIT (ORbits Extrapolation KIT) is a low level space dynamics library.
It provides basic elements (orbits, dates, attitude, frames ...) and
various algorithms to handle them (conversions, analytical and numerical
propagation, pointing ...).
/* Copyright 2002-2024 CS GROUP
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.attitudes;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldRotation;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Rotation;
import org.hipparchus.geometry.euclidean.threed.RotationConvention;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.frames.FieldTransform;
import org.orekit.frames.Frame;
import org.orekit.frames.Transform;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.FieldPVCoordinatesProvider;
import org.orekit.utils.PVCoordinatesProvider;
/**
* This class handles a spin stabilized attitude provider.
* Spin stabilized laws are handled as wrappers for an underlying
* non-rotating law. This underlying law is typically an instance
* of {@link CelestialBodyPointed} with the pointing axis equal to
* the rotation axis, but can in fact be anything.
* Instances of this class are guaranteed to be immutable.
* @author Luc Maisonobe
*/
public class SpinStabilized implements AttitudeProviderModifier {
/** Underlying non-rotating attitude provider. */
private final AttitudeProvider nonRotatingLaw;
/** Start date of the rotation. */
private final AbsoluteDate start;
/** Rotation axis in satellite frame. */
private final Vector3D axis;
/** Spin rate in radians per seconds. */
private final double rate;
/** Spin vector. */
private final Vector3D spin;
/** Creates a new instance.
* @param nonRotatingLaw underlying non-rotating attitude provider
* @param start start date of the rotation
* @param axis rotation axis in satellite frame
* @param rate spin rate in radians per seconds
*/
public SpinStabilized(final AttitudeProvider nonRotatingLaw,
final AbsoluteDate start,
final Vector3D axis, final double rate) {
this.nonRotatingLaw = nonRotatingLaw;
this.start = start;
this.axis = axis;
this.rate = rate;
this.spin = new Vector3D(rate / axis.getNorm(), axis);
}
/** {@inheritDoc} */
@Override
public AttitudeProvider getUnderlyingAttitudeProvider() {
return nonRotatingLaw;
}
/** {@inheritDoc} */
@Override
public Attitude getAttitude(final PVCoordinatesProvider pvProv,
final AbsoluteDate date, final Frame frame) {
// get attitude from underlying non-rotating law
final Attitude base = nonRotatingLaw.getAttitude(pvProv, date, frame);
final Transform baseTransform = new Transform(date, base.getOrientation());
// compute spin transform due to spin from reference to current date
final Transform spinInfluence =
new Transform(date,
new Rotation(axis,
rate * date.durationFrom(start),
RotationConvention.FRAME_TRANSFORM),
spin);
// combine the two transforms
final Transform combined = new Transform(date, baseTransform, spinInfluence);
// build the attitude
return new Attitude(date, frame,
combined.getRotation(), combined.getRotationRate(), combined.getRotationAcceleration());
}
/** {@inheritDoc} */
@Override
public Rotation getAttitudeRotation(final PVCoordinatesProvider pvProv, final AbsoluteDate date, final Frame frame) {
// get rotation from underlying non-rotating law
final Rotation baseRotation = nonRotatingLaw.getAttitudeRotation(pvProv, date, frame);
// compute spin rotation due to spin from reference to current date
final Rotation spinInfluence = new Rotation(axis, rate * date.durationFrom(start), RotationConvention.FRAME_TRANSFORM);
// combine the two rotations
return baseRotation.compose(spinInfluence, RotationConvention.FRAME_TRANSFORM);
}
/** {@inheritDoc} */
@Override
public > FieldAttitude getAttitude(final FieldPVCoordinatesProvider pvProv,
final FieldAbsoluteDate date,
final Frame frame) {
// get attitude from underlying non-rotating law
final FieldAttitude base = nonRotatingLaw.getAttitude(pvProv, date, frame);
final FieldTransform baseTransform = new FieldTransform<>(date, base.getOrientation());
// compute spin transform due to spin from reference to current date
final FieldTransform spinInfluence =
new FieldTransform<>(date,
new FieldRotation<>(new FieldVector3D<>(date.getField(), axis),
date.durationFrom(start).multiply(rate),
RotationConvention.FRAME_TRANSFORM),
new FieldVector3D<>(date.getField(), spin));
// combine the two transforms
final FieldTransform combined = new FieldTransform<>(date, baseTransform, spinInfluence);
// build the attitude
return new FieldAttitude<>(date, frame,
combined.getRotation(), combined.getRotationRate(), combined.getRotationAcceleration());
}
/** {@inheritDoc} */
@Override
public > FieldRotation getAttitudeRotation(final FieldPVCoordinatesProvider pvProv,
final FieldAbsoluteDate date,
final Frame frame) {
// get attitude from underlying non-rotating law
final FieldRotation baseRotation = nonRotatingLaw.getAttitudeRotation(pvProv, date, frame);
// compute spin rotation due to spin from reference to current date
final FieldRotation spinInfluence =
new FieldRotation<>(new FieldVector3D<>(date.getField(), axis),
date.durationFrom(start).multiply(rate),
RotationConvention.FRAME_TRANSFORM);
// combine the two rotations
return baseRotation.compose(spinInfluence, RotationConvention.FRAME_TRANSFORM);
}
}